1. Field of the Invention
This invention relates to a method for treating a substrate, a method for conveying a substrate, and an apparatus for conveying a substrate which are used for lithography process or the like in semiconductor device production.
2. Background Art
In a semiconductor lithography technique, as the pattern structure is finer, fine pattern exposure using extreme ultraviolet (EUV) light near 13.5 nm has been developed.
The EUV light has intensive attenuation in an air, and damage is caused in an optical system by active species generated by moisture excited in an atmosphere, and therefore, the exposure is performed in high vacuum of, for example, the vicinity of 10−5 Pa (pascal).
Moreover, because it has been estimated that the apparatus price of the EUV exposure apparatus becomes very high, high throughput such as 100 wafers per hour in a substrate (wafer) having a diameter of 300 mm is required for the EUV exposure apparatus. Therefore, it is necessary that conveyance of substrate into the EUV exposure apparatus and adjustment of atmospheric pressure in the exposure apparatus along therewith are performed at high speed.
On the other hand, along with conveying the substrate from an application development apparatus or the like to the inside of the exposure apparatus, the degree of vacuum of the inside of the exposure apparatus is shifted, and thereby, temperature changes inside the exposure apparatus and of the substrate and additional humidity change are caused. For ensuring adjustment accuracy and focus accuracy in the exposure that are required for a fine pattern to be formed by the EUV exposure apparatus, it is necessary to suppress the above-described fluctuation of the degree of vacuum and the humidity.
The most simple method for suppressing the pressure change is to control the degree of vacuum (and humidity) inside an interface for conveying the pre-exposure substrate into the exposure apparatus to be equal to that of the inside of the exposure apparatus, and then, to carry the pre-exposure substrate into the exposure apparatus, and to carry the substrate out of the exposure apparatus to the interface.
However, it is difficult in a conventional interface structure to maintain the high throughput with adapting the pressure of the interface to that of the inside of the exposure apparatus.
In a lithography process by EUV light, after subjecting the substrate to be processed to application of resist material and bake treatment and cooling treatment at room temperature (treatment for cooling temperature) in an application and development apparatus, the substrate on which the resist film is formed is stored in a buffer and the exposure is waited for. The pre-exposure substrate is conveyed from the application and development apparatus into the exposure apparatus by the interface, and subjected to exposure treatment on an exposure stage in the exposure apparatus, and then, conveyed into the application and development apparatus again, and subjected to post-exposure bake treatment, cooling treatment (temperature-lowering treatment), and development treatment, and thereby, a resist pattern is formed.
When the substrate to which a resist material is applied is put into the vacuum chamber containing the exposure stage and exposed, occasionally, foreign material attached onto the resist surface fries to cause contamination of, inner wall in the vacuum chamber, light path, or mirror. In many cases, the foreign matter is organic matter, but if the substance thereof contaminates the chamber or the light path or the mirror, illuminance of EUV light lowers and the throughput lowers, or aberration is caused and lowering of resolution performance is caused.
If chamber or light path or mirror or exposure stage in the vacuum regions in the exposure apparatus is contaminated, it becomes necessary that the vacuum is once released and the maintenance such as cleaning or component replacement is performed, and therefore, the downtime of the exposure apparatus becomes long, and the contamination becomes a factor of pushing up the cost of the semiconductor device production.
Moreover, if moisture is attached to the substrate to which the resist is applied, there are caused the problems that the degree of vacuum of the vacuum chamber into which the exposure stage is placed fluctuates to lower the throughput because the exposure cannot be performed for the time in which the degree of vacuum is being stabilized and that the water molecule in the vacuum chamber is irradiated with EUV light to be ionized and the performance of parts are degraded if the ionized water molecule attaches to the exposure apparatus again.
Therefore, it is necessary to administer the moisture attaching to the pre-exposure substrate to be a low moisture amount.
A technique for detecting contamination in the EUV exposure apparatus and cleansing the contamination is disclosed in JP-A 2002-261001 (Kokai), and a technique for lowering contamination by applying charge attracting particles in the exposure apparatus is disclosed in JP-A 2006-32957 (Kokai), and a technique for cleaning up a mirror in the EUV apparatus is disclosed in JP-A 2005-268358 (Kokai). However, in every one of the techniques, an apparatus enabling a special rinsing method in the exposure apparatus is required in the exposure apparatus, and therefore, such an apparatus becomes a factor pushing up the apparatus price.
Moreover, a technique for solving the problem by applying a top coat onto the resist for preventing the illuminance from being degraded due to generation of moisture in irradiating the resist with the EUV light and attachment of the moisture to the mirror is disclosed in JP A-2004-348133 (Kokai), but because a protective film is formed by CVD deposition, there are problems that the process cost is pushed up and that the time for pulling and putting the substrate after the resist application becomes long and that the performance of the resist is degraded by CVD deposition film and so forth.